A 39-year-old man, who died following a three-car collision on the N4 dual carriageway near Mullingar, was driving on the wrong side of the road, gardaí said.
Gardaí received reports a car was travelling in the wrong direction for nearly 50km, and at speed of over 120km/h before the crash.
Six other people were injured in the collision, which occurred on the Sligo to Dublin road at around 2pm.
The man's body was removed to the Midland Regional Hospital, Mullingar, for a post-mortem examination.
The six people travelling in the other cars were brought to hospitals in Mullingar and Tullamore.
Their injuries are not thought to be life-threatening.
Gardaí are appealing for witnesses to contact them at Mullingar Garda Station on 044-9384000.
